(1) Field of the Invention
The present invention relates to an apparatus for controlling the fuel injection quantity at the start of a two-cycle engine. More particularly, the present invention relates to a system for controlling the fuel injection quantity at the start of a two-cycle engine of the type where a fuel is preliminarily injected before the revolution of the engine for shortening the time required for starting the engine, wherein the preliminary injection is appropriately performed to improve the startability.
(2) Description of the Related Art
As the 2-cycle engine for a two-wheeled vehicle or a snow mobile, there has been adopted an engine of the fuel supply system where injection of a fuel is electronically controlled by using a fuel injection valve (see, for example, Japanese Unexamined Patent Publication No. 63-255543). For example, there can be mentioned a system in which a fuel injection valve is arranged in an intake manifold zone of each cylinder and injection is simultaneously effected in all of the cylinders.
In such a two-wheeled vehicle of the electronically controlled fuel injection system, in order to improve the startability, the fuel injection quantity at the start is controlled so that the fuel injection quantity at the start is a little larger than the normal fuel injection quantity.
For example, at the start of an ignition switch, that is, at the time of cranking, a value computed according to the following equation is outputted: EQU Ti=Tcs.times.K.sub.1 .times.K.sub.2
wherein Ti represents the width of the injection pulse at the start, Tcs represents the basic fuel injection quantity, K.sub.1 represents the revolution speed correction coefficient, and K.sub.2 represents the time correction coefficient.
The basic fuel injection quantity at the start is an injection quantity stored in advance according to the engine temperature, the revolution correction coefficient is a coefficient changing according to the cranking revolution speed, and the time correction coefficient is a coefficient changing according to the cranking time.
In this two-cycle engine, since the fuel injection is effected in the intake manifold portion, the fuel becomes viscous, especially at a low temperature, and therefore, a long time is required for the fuel to travel to a combustion chamber and a long time is required for starting the engine.
As means for overcoming this disadvantage, there has been adopted a method in which the fuel is preliminarily injected while the engine is not rotated, that is, the fuel is injected at a time when a key switch is turned on (when a power source is turned on) (see Japanese Examined Patent Publication No. 47-16212). According to this control method, injection is effected when the key switch is turned on, irrespectively of the driver's intention.
Accordingly, for example, in the case where even if the key switch is turned on, it is only for listening on the radio and the engine is not started, or in the case where the key switch is frequently turned on and off by the drive's habitual practice, the fuel is unnecessarily injected and spent. Accordingly, this method cannot be regarded as an appropriate control method.